Director: Ira Sachs
Cast: Thure Lindhardt, Zachary Booth
Certificate: 18

When a film starts in a dimly lit room with a man on the phone to a sex hotline, you know you’re in for a happy hour and a half. That grubby realism is what defines Ira Sachs’ frank romance. Struggling director Erik (Lindhardt) and city lawyer Paul (Booth) may hook up early on and send sparks flying, but it's not long until Paul’s drug addiction rears its head. He disappears for days on end, leaving his needy other half waiting by the door. But while Erik keeps the lights on, Ira Sachs refuses to dial down the darkness; this is cinema at its most painful.

That may not appeal to everyone, of course, but Sachs’ achievement is not to get too bogged down in the sadness. The film wallows from time to time, but keeps itself restrained. Even its 18-certificate sex scenes are graphic but never sleazy or overplayed.

The result is a provocative look at a broken relationship, full of angst – most of it Erik’s. As the clingy, nervous lover, Lindhardt is astonishing, capturing a sense of vulnerability that suggests his own personal experience; that same feeling permeates Mauricio Zacharias and Ira Sachs’ screenplay, given a grainy honesty thanks to DoP Thimios Bakatakis, who shoots it all on Super 16mm.

Minor problems linger beneath the surface. Zachary Booth’s performance is impressive, but his character is harder to engage with; we understand Erik’s generous admirer, but Paul never becomes more than the distant object of his affection. And yet that also works in the film’s favour, focusing on the impact of Paul’s heroin habit on those around him, rather than his own battle. It’s a film about devotion rather than addiction – and that’s what makes it so devastating.

Comparisons are easy to draw between this and last year’s similarly honest Weekend. Andrew Haigh’s film may be the superior piece, but Keep the Lights retains its intimacy while zooming out to look at a couple’s bigger picture, chronicling eight years of on-and-off uncertainty. The title cards are annoyingly intrusive, but the emotional impact is no less powerful.

"I'm glad to see you,” says one when the pair reunite after one long interlude. "Are you?" comes the reply. It rings with autobiographical truth. Erik plays a documentary filmmaker; Sachs might as well be one too.